Characterization of Proteinaceous Membrane Foulants from Whey Ultrafiltration

Abstract

Cheddar cheeses were made using calf rennet and Mucor pusillus protease. The resultant wheys were processed with a pilot-scale, plate and frame UF system, which contained negatively charged, 10-kdal (nominal) cutoff, polysulfone membranes. In addition, whey from cheese making using calf rennet was treated with Mucor pusillus protease prior to UF. After whey UF, the proteinaceous fraction of the membrane foulants was isolated and analyzed by SDS-PAGE.Alpha-lactalbumin and several peptides in whey adsorb preferentially onto the surface and foul the UF membranes. Foulant isolated from UF membranes used to process whey from cheese making using calf rennet contained significant amounts of 13.5-kdal and 18 to 22-kdal peptides that appear to be casein proteolysis products. These peptides were not detectable in the unprocessed wheys or in the membrane foulants from UF of whey form cheese making using Mucor pusillus protease. Permeate flux during UF of whey from cheese making using calf rennet was significantly lower than permeate flux of whey from cheese making using Mucor pusillus protease.When the whey from cheese making with calf rennet was treated with Mucor pusillus protease before UF, permeate flux was improved by 40% when compared with that of untreated whey. Membrane foulants from UF of this whey did not contain the 13.5 and 18 to 22-kdal peptides.Our results indicate that low permeate flux during UF of whey from cheese making using calf rennet is associated with adsorption of various peptides to the UF membrane. Mucor pusillus protease fragmented many of these peptides in whey from cheese making using calf rennet and increased permeate flux to levels comparable to permeate flux during UF of whey from cheese making using Mucor pusillus protease.